| Albans Capital Limited | Professional & scientific | 2011 |
| Albion Close 05/10/56 Limited | Extraterritorial | 2013 |
| Albion Dominion Corporate Partners Limited | Financial services | 2025 |
| Albion Sussex Capital Partners Limited | Financial services | 2025 |
| Alchemy Award Limited | Professional & scientific | 2006 |
| Alda Property Limited | Construction | 2012 |
| Aldbury Capital Limited | Financial services | 2019 |
| Aldeburgh Trading Company Limited | Administrative & support | 2002 |
| Aldermere (Cheshunt) Management Company Limited | Households | 2010 |
| Aldridge Analytical Engineering Services Limited | Professional & scientific | 2023 |
| Aldykes Management Limited | Households | 2008 |
| Alemania Limited | Professional & scientific | 2018 |
| Alex Caine Ltd | Financial services | 2012 |
| Alexander Machinery Limited | Agriculture & fishing | 2015 |
| Alfa Design Group Limited | Professional & scientific | 2016 |
| Alice Limited | Manufacturing | 2016 |
| Alison Haynes Skin Clinic Limited | Administrative & support | 2022 |
| Alkaline Properties Ltd | Real estate | 2019 |
| ALL 2 Gain Limited | Professional & scientific | 2023 |
| ALL for Sport Limited | Education | 2006 |
| ALL Property Buyer Limited | Real estate | 2009 |
| ALL4SPORT Limited | Education | 2007 |
| Allan Reece Associates LLP | | 2017 |
| Allan Reece Properties Limited | Real estate | 2014 |
| Allbikeparts Limited | Wholesale & retail | 2012 |
| Alliance Cleaning (Holdings) Limited | Extraterritorial | 2008 |
| Alliance Cleaning Limited | Administrative & support | 1998 |
| Alliance Facilities Solutions Limited | Extraterritorial | 2015 |
| Alliance Haus Limited | Real estate | 2017 |
| Alliance Supply Co Limited | Wholesale & retail | 2024 |
| Alliance Unit Ltd | Real estate | 2022 |
| Allington Healthcare Limited | Health & social care | 1999 |
| Aloxar Capital Ltd | Financial services | 2018 |
| Aloxar Investments Ltd | Financial services | 2019 |
| Aloxar Ventures Ltd | Financial services | 2020 |
| ALP Investments Limited | Administrative & support | 2012 |
| Alpha Heritage Care Ltd | Health & social care | 2023 |
| Alpha Heritage Ltd | Wholesale & retail | 2021 |
| Alphachain Traders Ltd | Education | 2020 |
| Alphanumeric Consulting Limited | Professional & scientific | 2017 |
| Alpin Engineering Ltd | Construction | 2024 |
| Alstrom Limited | Construction | 2017 |
| Altherm System Build Limited | Wholesale & retail | 2025 |
| Altigo Ltd | Other services | 2009 |
| Aluminium Profile Supplies Limited | Administrative & support | 2012 |
| AM Parcel Services Ltd | Transport & logistics | 2026 |
| Amanda GAY Limited | Other services | 2007 |
| AMB Heating Limited | Construction | 2021 |
| Amber Mortgage Solutions Limited | Financial services | 2007 |
| Ambr Ltd | Professional & scientific | 2020 |
| AMG Estates Group Ltd | Real estate | 2025 |
| AMG Residential Ltd | Real estate | 2024 |
| Amhurst Catering Limited | Hospitality | 2018 |
| Amiae Ventures Ltd | Financial services | 2026 |
| Ammeraal Beltech UK Holding Limited | Financial services | 2016 |
| Ammerex Ltd | Wholesale & retail | 2008 |
| Amolec Electrical Services Limited | Construction | 2021 |
| Amtrom Limited | Administrative & support | 2017 |
| Amwell Electrical Limited | Construction | 1975 |
| Amwell Heath Construction Ltd | Construction | 2024 |
| Amwell House Developments Limited | Real estate | 2018 |
| Amwell Management Company Limited | Real estate | 1993 |
| Amwell Spring Consulting Limited | Professional & scientific | 2019 |
| Amyb Installation Ltd | Construction | 2019 |
| Amzware Ltd | Wholesale & retail | 2022 |
| AN Islington Hooligan Film Ltd | Information & communication | 2025 |
| Anaconda Capital Limited | Administrative & support | 2020 |
| Anava Limited | Wholesale & retail | 2017 |
| Anchor Terrace Freehold Limited | Households | 2017 |
| Andrew Benton Limited | Construction | 1968 |
| Andrew Jackson UK Limited | Wholesale & retail | 2009 |
| Andrew John Smith Ltd | Extraterritorial | 2022 |
| Andrews & Co. Lettings & Management Limited | Real estate | 2004 |
| Andusia Hazchem Treatment Limited | Water & waste | 2015 |
| Andusia Holdings Limited | Financial services | 2019 |
| Andusia Limited | Water & waste | 2019 |
| Andusia Management Limited | Wholesale & retail | 2014 |
| Andusia Recovered Fuels Ltd | Wholesale & retail | 2012 |
| Andusia Resource Recovery Limited | Wholesale & retail | 2016 |
| Andy Goode Design Ltd | Professional & scientific | 2017 |
| Anek Media Limited | Information & communication | 2024 |
| Angela Clark Ltd | Extraterritorial | 2016 |
| Angels & Ledgers Ltd | Professional & scientific | 2018 |
| Anglo Commerce Ltd | Professional & scientific | 2017 |
| Anjana Trehan Property Developments Limited | Real estate | 2020 |
| Annabell Bluebell Limited | Arts & recreation | 2008 |
| Another Word Communications Limited | Professional & scientific | 2015 |
| Anthony Judkins Ltd | Administrative & support | 2016 |
| Anthony Oakden & Sons Limited | Financial services | 2023 |
| Anticlimax Ltd | Manufacturing | 2024 |
| Antler Consulting (Hertford) Ltd | Professional & scientific | 2022 |
| Anvil Audio Ltd | Arts & recreation | 2016 |
| ANY Bath.Com Limited | Construction | 2006 |
| ANY Day Roofing Ltd | Construction | 2024 |
| ANY Day Scaffolding Ltd | Construction | 2022 |
| ANY Day Scaffolding Ltd (UK) Ltd | Construction | 2026 |
| Anyflex Ltd | Professional & scientific | 2025 |
| AOH Consulting Ltd | Information & communication | 2016 |
| Aoifemay Limited | Professional & scientific | 2018 |
| Apex Surveyance Ltd | Professional & scientific | 2026 |